Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.84	9.551%	$191.539	$191.54	$191.55	$191.50
Purchase #2	$26.75	13.503%	$30.3621	$30.36	$30.35	$30.40
Purchase #3	$40.49	8.403%	$43.8924	$43.89	$43.90	$43.90
Purchase #4	$152.86	12.182%	$171.4814	$171.48	$171.50	$171.50
Purchase #5	$161.94	6.298%	$172.139	$172.14	$172.15	$172.10
Purchase #6	$74.90	5.673%	$79.1491	$79.15	$79.15	$79.10
Purchase #7	$164.28	3.725%	$170.3994	$170.40	$170.40	$170.40
7 purchase totals =	$796.06		$858.9624	$858.96	$859.00	$858.90